The United States Equal Employment Opportunity Commission enforces the federal law that prohibits discrimination. You can reach them at http://www.eeoc.gov/
The United States Department of Labor enforces many federal employment laws including the federal minimum wage and overtime laws. You can reach them at http://www.dol.gov/
The National Labor Relations Board enforces federal laws that apply to people who work for the private sector. These laws also apply to the relationship between employees and their labor unions. You can reach them at http://www.nlrb.gov/nlrb/home/default.asp